In recent years there has been increasingly widespread use of a technique for obtaining white light-emitting diodes (LEDs) by arranging an yttrium aluminum garnet (YAG) phosphor or other type of phosphor in the vicinity of a gallium nitride (GaN)-based blue LED chip, and color-mixing the blue light emitted from the blue LED chip and yellow light emitted by secondary emission upon the phosphor receiving the blue light.
With a white LED of such description, there is generally employed a method for using a transparent resin throughout which the phosphor has been dispersed, to seal in an LED chip and/or a mounting part. However, the specific gravity of the phosphor is greater than that of the transparent resin, and accordingly there is settling of the phosphor before the resin has cured, which causes color unevenness during light emission, among other problems.
In view whereof, there have been a variety of proposed methods for suppressing the settling of the phosphor to prevent the occurrence of color unevenness. For example, as recited in Patent Citation 1, a silicone resin having a viscosity of 100 to 10,000 cP during resin curing is used as a sealing body to suppress settling and/or segregation of the phosphor. Patent Citation 2 discloses a chip component-type LED in which an LED element is disposed between an upper end opening and a lower end opening of a cylindrical container, which is filled with a light-transmissive resin from the upper end opening to the lower end opening, and an inner wall surface of the container is formed such that emitted light from the LED element is reflected toward the upper end opening.
Patent Citation 3 discloses a light-emitting device, as well as a method for producing same, in which a lipophilic compound made by adding organic cations to a layered compound primarily composed of a clay mineral is added to a liquid light-transmissive sealing material, as an anti-settling agent for the phosphor. Patent Citation 4 discloses a semiconductor light-emitting device in which a glass material or a glass material composed of a ceramic precursor polymer is used as a light-transmissive sealing material.